The present disclosure is related to the subterranean drilling and, more specifically, utilizing electrical impulses to break rock while drilling.
During subterranean drilling and completion operations, a pipe or other conduit is lowered into a borehole in an earth formation during or after drilling operations. Such pipes are generally configured as multiple pipe segments to form a “string”, such as a drill string or production string. As the string is lowered into the borehole, additional pipe segments are coupled to the string by various coupling mechanisms, such as threaded couplings.
During drilling, a bit is coupled to a leading end of the drill string. Due to rotation of the string or the rotation of a mud motor (or both) the bit is caused to rotate and crush or otherwise break rock or other materials that it contacts. The crushed rock is then removed to the surface by a drilling fluid pumped through the drill string to region at or near the drill bit. Such drilling relies on pressure and contact between the rock and drill bit to crush/break the rock. Several different types of drill bits that can accomplish such rock breaking are known and include, for example, rolling cutter bits that drill largely by fracturing or crushing the formation with “tooth” shaped cutting elements on two or more cone-shaped elements that roll across the face of the borehole as the bit is rotated. Another type of bit is a fixed cutter bit that employs a set of blades with very hard cutting elements, most commonly natural or synthetic diamond, to remove material by scraping or grinding action as the bit is rotated.
Another approach to crushing rock includes application of high-voltage electrical pulses to the rock to crush or break the rock. One such approach causes plasma-channel formation inside the rock ahead of the drill region due the application of high voltage pulses. The extremely rapid expansion of this plasma channel within the rock, which occurs in less than a millionth of a second, causes the local region of rock to fracture and fragment. This and other approaches may include providing electrodes at the tip bottom hole assembly (BHA). The BHA includes electronics that deliver the pulses to the electrodes and the discharge that causes the rock to break occurs through the rock and/or drilling fluid between the electrodes.
Electrodes and rock have to be electrical contacted only. Less or no weight on bit is required to maintain the electrical contact and the drilling process therefore. Drilling to vertical depth deeper than 30.000 ft (10.000 m) and extreme long laterals will be enabled due to the absence of heavy weight drill pipes within the BHA. The utilization of deep high enthalpy reservoirs, as environmental friendly energy source, will be possible in the future including the build of down hole heat exchangers with multiple lateral wellbores in crystalline rock.